1. Field of the Invention
The present invention relates to a fastening device with tape to which a fastener such as a male or female snap fastener made of thermoplastic resin material is integrally molded on and through front and rear surfaces of the tape. More particularly, it relates to a fastening device with tape which is a knitted tape having flexibility, some extent of stretching property, and form stability, and is ensured in dimensional stability during molding, and which is capable of following stretch of the attachment object sufficiently so that sewing on a curved portion can be neatly done.
2. Description of the Related Art
Most tapes to be used for a fastening device with tape, to which a fastener made of thermoplastic synthetic resin is attached integrally to the tape, are fabric woven with non-stretchable warp and weft yarns. The reason is that when the fasteners such as snap fasteners and eyelets are molded on a tape or the fastening device with tape is attached to an attachment object such as clothes, bag, curtain or the like, stability of the tape form is secured. Therefore, in general, the fastening device with tape has a low stretching property.
A production method for such a fastening device with tape has been disclosed in, for example, the U.S. Pat. No. 2,821,764. According to the production method, for a purpose of ensuring an excellent joining force between the tape and a grommet, a plurality of small holes are made around a mounting hole which is for mounting the grommet and inserting a tape, and the grommet to be molded integrally on front and rear surfaces of the tape through the mounting hole is fixed firmly with leg portions formed through those small holes. According to a specification of the U.S. patent, in order to prevent waving of a peripheral portion around the mounting hole of the tape or displacement of the tape in directions of the front and rear surfaces thereof, a plurality of pin members are provided inside a grommet-molding cavity formed in a movable die and a fixed die such that they are protruded into portions in which the peripheral portion around the mounting hole of the tape is inserted from each of inner faces of the cavities so as to oppose each other. Then, the peripheral portion around the mounting hole of the tape is clamped by the pin members. Under this condition, molten resin material is injected so as to mold the eyelet integrally around the mounting hole of the tape. Such a structure for preventing the waving has been also applied to a production method for a snap fastener with tape, which is disclosed in, for example, Japanese Patent Laid-Open Publication No. 62-155805.
According to Japanese Utility Model Laid-Open Publication No. 56-16311 and Japanese Patent Laid-Open Publication No. 10-33211, the tape is composed of woven fabric or knitted fabric, a fastener molding portion formed in a center in a width direction of the tape is formed by weaving or knitting coarsely, at least, and the snap fastener is molded integrally on that center portion. In this case, the mounting holes are not made in the fastener molding portion as in the aforementioned U.S. patent, but the snap fastener is molded integrally on the front and rear surfaces of the tape by introducing molten resin material through gaps between yarns woven or knitted coarsely in the tape.
The aforementioned synthetic resin fastening device with tape, which substitutes for a conventional fastening device with tape to which a metallic fastener is attached, is excellent to the touch as well as productivity. Thus, this is not only applied to the fastening devices in outer wears, various bags or the like, but also often used for foundation, inner wear, baby clothes, medical clothes or the like, which directly contacts the skin of man's body. On the other hand, recently, various fabric materials have been developed to meet diversified fashions. For example, there are used outer wear having a stretching property, various kinds of clothes made of fabric material having softness and an appropriate stretching property, knitted fabric or the like are used.
Usually, a woven tape as mentioned above is used for a tape of a synthetic resin fastening device with tape which is applied to clothes to be directly in contact with man's skin like foundation or the clothes made of peculiar fabric material. However, the woven fabric tape does not fit to such soft clothes having ample stretching property, so that it is likely to move individually between the clothes and the fasteners. Therefore, when the fastening device is engaged or disengaged, it is difficult to join a male and a female fasteners with fingers, or a finger force of the operation is difficult to transmit to each of the fasteners. As a result, it takes a long time to engage or disengage the both fasteners.
Even if, a flexible, thin woven tape is used, excellent stretching property cannot be expected. When this kind of the woven tape is attached to stretchable clothes or along a curved portion of the clothes, the tape is not capable of following the stretching of the stretchable clothes, the tape is wrinkled when it is sewn to the curved portion, or the curved portion of the sewing portion loses its shape.
As a tape material for a fastening device with tape which is suitable for attachment to a curved portion, Japanese Utility Model Publication No. 3040449 proposes use of bias woven fabric which is obtained by cutting warp and weft yarns obliquely at a predetermined angle. However, in the bias woven fabric, the yarns tend to be frayed at a cut end thereof. Therefore, according to the registered utility model, both edge portions in the width direction of the tape is folded back toward its center, and the synthetic resin snap fastener is molded integrally between those opposing edge portions.
Although use of a knitted tape has been described in the above mentioned Japanese Utility Model Laid-Open Publication No. 56-16311 and Japanese Patent Laid-Open Publication No. 10-33211, its concrete tape structure relating to a knitting structure, thickness of yarn to be used or the like has not been concretely proposed. In the synthetic resin fastening device with tape using the bias woven fabric tape as disclosed in the Japanese Utility Model Publication No. 3040449, no concrete method has been disclosed about a production method for the synthetic resin fastening device with tape, particularly a molding method for the fastening device.
Conventionally, as a tape material for the synthetic resin fastening device with tape of this kind, many attempts have been carried out in order to use stretchable tapes, such as a knitted tape using a stretching property based on its knitting structure, a woven tape using stretchable yarns as constitutive yarns of warp yarns. However, because many problems, that will occur when the synthetic resin fasteners are molded integrally on the tape, have not been overcome as described later, these tapes have not been reduced to practice. Even when the knitted tape is used, it is not capable of securing form stability as well as the woven tape. In order to secure this form stability, it is necessary to suppress that stretching property completely by, for example, coating the knitting structure. However, when the stretching property is suppressed completely, proper flexibility and stretching property of the knitted fabric are not exerted so that the above requirement cannot be satisfied.
In general, in production of this kind of synthetic resin fastening device with tape, a tape is inserted into a tape insertion passage in upper and lower dies formed with a molding cavity for molding a fastener, at facing portions thereof, and thermoplastic synthetic resin is injected into the cavity in molten state so as to mold the fastener on front and rear surfaces of the tape, as described above. In order to mold the fastener on the front and rear surfaces of the tape, generally a fastener-mounting hole is made in the center portion in the width direction of the tape, or the tape is knitted with a coarse knitting structure, in case where the molten resin is introduced into the cavity in the upper and lower dies disposed so as to sandwich the front and rear surfaces of the tape.
The aforementioned fastener is molded integrally by injecting molten resin material successively at a predetermined pitch to a long tape being transferred between the upper and lower dies intermittently. Mounting positions of the male and female fasteners on each tape need to be precise enough to correspond to each other in the synthetic resin fastening device with tape which acts in a pair as the male and female fastening device with tape as a product. That is, an error in pitch between the plural fasteners molded on the tape should be avoided.
However, although in case of the knitted fabric having stretching property, some extent of stretching property may be obtained easily due to its structure, it is difficult to obtain form stability which is a conflicting function to the stretch property. Thus, to mold plural fasteners continuously at an accurate pitch on front and rear surfaces of a knitted tape, not only a highly accurate control on a tape tension, transfer speed but also high positioning accuracy is required. To satisfy these requirements, a highly accurate control technology and equipment for such flexible material are necessary. However, even when these are technologically possible to be achieved, they cannot be carried out in economical viewpoints.
Particularly, when a fastening device with tape having low stretching property is sewed to and along a curved opening/closing portion of clothes, the tape may be wrinkled or the curve line of the opening/closing portion may lose its shape. To eliminate this disadvantage, use of the bias woven fabric as a tape, which is disclosed in the aforementioned Japanese Utility Model publication No. 3040449, can be considered. However, warp yarn and weft yarn tend to be loose at an edge portion of the bias woven fabric. Therefore, both the edge portions in the tape width direction are folded toward the center as described above, and a fastener is molded integrally along the opposing edge portions so as to prevent the yarns from being loose.
Therefore, the production method includes additional steps to ordinary production steps, for example, for producing a tape by bias-cutting a woven fabric, folding the tape back from the right and left along a longitudinal direction thereof and introducing the tape to an injection molding machine for molding a fastener. Therefore, not only production equipment necessarily increases but also productivity drops remarkably. Further, because a tape obtained by the bias-cut has a stretching property both in the warp and weft directions, it cannot be introduced into the injection molding machine at an accurate pitch. To carry out positioning of the tape, complicated mechanism and control are required. Further, the tape of the fastening device with tape as a product becomes cylindrical so that its form is not stabilized. When it is intended to sew the tape neatly, the sewing procedure becomes troublesome.